Similes and metaphors should be unique to your characters and worlds and can be very effective in helping build both.
Similes and metaphors are extremely useful in descriptions.
Consider: The sky is blue. Kind of boring, right?
In comparison, let's look at a couple similes...
The sky is as blue as a mother's tears.
The sky is as blue as mermaids' scales.
Wow. Those bring to mind two totally different images and are much more descriptive than the declarative statement.
Consider using similes and metaphors in your writing!
FYI the next Electric Spec submission deadline is coming up: October 15, 2016. Get those stories in!